

function LBXCustomBase() {

    var _PADCHAR = "=",
            _ALPHA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",

            _VERSION = "1.0";


    function _getbyte64( s, i ) {
        // This is oddly fast, except on Chrome/V8.
        // Minimal or no improvement in performance by using a
        // object with properties mapping chars to value (eg. 'A': 0)

        var idx = _ALPHA.indexOf( s.charAt( i ) );

        if ( idx === -1 ) {
            throw "Cannot decode base64";
        }

        return idx;
    }

    //+ (void)initCustomEncodeChars:(const char*)base64EncodeChars paddingChar:(char)paddingChar
    function _initCustomEncodeChars(base64EncodeChars,paddingChar) {

        if (base64EncodeChars)
            _ALPHA = base64EncodeChars;
        if (paddingChar)
            _PADCHAR = paddingChar;

    }


    function _decode( s ) {
        var pads = 0,
                i,
                b10,
                imax = s.length,
                x = [];

        s = String( s );

        if ( imax === 0 ) {
            return s;
        }

        if ( imax % 4 !== 0 ) {
            throw "Cannot decode base64";
        }

        if ( s.charAt( imax - 1 ) === _PADCHAR ) {
            pads = 1;

            if ( s.charAt( imax - 2 ) === _PADCHAR ) {
                pads = 2;
            }

            // either way, we want to ignore this last block
            imax -= 4;
        }

        for ( i = 0; i < imax; i += 4 ) {
            b10 = ( _getbyte64( s, i ) << 18 ) | ( _getbyte64( s, i + 1 ) << 12 ) | ( _getbyte64( s, i + 2 ) << 6 ) | _getbyte64( s, i + 3 );
            x.push( String.fromCharCode( b10 >> 16, ( b10 >> 8 ) & 0xff, b10 & 0xff ) );
        }

        switch ( pads ) {
            case 1:
                b10 = ( _getbyte64( s, i ) << 18 ) | ( _getbyte64( s, i + 1 ) << 12 ) | ( _getbyte64( s, i + 2 ) << 6 );
                x.push( String.fromCharCode( b10 >> 16, ( b10 >> 8 ) & 0xff ) );
                break;

            case 2:
                b10 = ( _getbyte64( s, i ) << 18) | ( _getbyte64( s, i + 1 ) << 12 );
                x.push( String.fromCharCode( b10 >> 16 ) );
                break;
        }

        return x.join( "" );
    }


    function _getbyte( s, i ) {
        var x = s.charCodeAt( i );

        if ( x > 255 ) {
            throw "INVALID_CHARACTER_ERR: DOM Exception 5";
        }

        return x;
    }


    function _encode( s ) {
        if ( arguments.length !== 1 ) {
            throw "SyntaxError: exactly one argument required";
        }

        s = String( s );

        var i,
                b10,
                x = [],
                imax = s.length - s.length % 3;

        if ( s.length === 0 ) {
            return s;
        }

        for ( i = 0; i < imax; i += 3 ) {
            b10 = ( _getbyte( s, i ) << 16 ) | ( _getbyte( s, i + 1 ) << 8 ) | _getbyte( s, i + 2 );
            x.push( _ALPHA.charAt( b10 >> 18 ) );
            x.push( _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) );
            x.push( _ALPHA.charAt( ( b10 >> 6 ) & 0x3f ) );
            x.push( _ALPHA.charAt( b10 & 0x3f ) );
        }

        switch ( s.length - imax ) {
            case 1:
                b10 = _getbyte( s, i ) << 16;
                x.push( _ALPHA.charAt( b10 >> 18 ) + _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) + _PADCHAR + _PADCHAR );
                break;

            case 2:
                b10 = ( _getbyte( s, i ) << 16 ) | ( _getbyte( s, i + 1 ) << 8 );
                x.push( _ALPHA.charAt( b10 >> 18 ) + _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) + _ALPHA.charAt( ( b10 >> 6 ) & 0x3f ) + _PADCHAR );
                break;
        }

        return x.join( "" );
    }


    return {
        decode: _decode,
        encode: _encode,
        initCustomEncodeChars:_initCustomEncodeChars,
        VERSION: _VERSION
    };
}
